Add composer 2.0 support

[hgajjar]

Composer 2 has been releases recently. However, there are some old plugins in composer 1 which does not support composer 2 yet.

So instead of upgrading the existing composer version in base image, we need to see how we can provide support for composer 2 as an option, so that projects can make use of it if their framework/project supports it.

I have opened this issue agains base harness repo, but it might be that we need to make this change in php base image.